MORPHOLOGICAL CHARACTERIZATION BY SCANNING ELECTRON MICROSCOPY (SEM) OF COMPOSITE ADSORBENTS DERIVED FROM PLANT HUSK WASTE: A BASIS FOR DEVELOPING ECO-FRIENDLY MATERIALS FOR POLLUTANT ADSORPTION

Abstract

This study investigates the morphological features, obtained by scanning electron microscopy (SEM), of individual activated carbons prepared from agricultural and fruit-processing wastes apricot stone shells, walnut shells and grape seed shells and of their three-component composite adsorbent. The samples were pyrolysed at 600 °C in an inert atmosphere, chemically activated with KOH, and converted into a composite by mechanical mixing in an equal mass ratio (1:1:1) followed by a secondary heat treatment (300 °C). SEM analysis revealed that each precursor forms a distinct carbon skeleton: the apricot pyrolysate showed an open cellular (honeycomb-like) structure (cell density 400–600 cells/mm²), the walnut pyrolysate a dense sponge-like 3D-interconnected structure (800–1000 cells/mm²), and the grape pyrolysate a lamellar (plate-like) and “Swiss-cheese” morphology. KOH activation opened the cell walls in all samples and generated submicron pores (200–500 nm). The composite developed a hybrid “cheese–cellular–plate” morphology, absent in any individual component, together with a zone rich in uniformly sized (1–2 µm) circular pores, which morphologically confirms the synergistic effect of compositing. The resulting granular commercial form (0.3–0.8 mm) indicates the potential of the composite for industrial-scale application.